2.5. TFIIH functions as a ubiquitin ligase in DNA damage repair
The TFIIH complex contains E3 ubiquitin (Ub) ligase activity, which
primarily resides within the p44 subunit (Ssl1 in yeast) in the ring
finger domain (RNF) (Takagi et al., 2005). The p44 subunit is known for
its role in the enhancement of XPD helicase activity in the NER pathway,
but this E3 Ub ligase activity is interesting in the context of TFIIH’s
role in both NER and transcription. It is noted that RNA Pol II is
ubiquitinated during transcription and during repair; however, the
evidence suggests that this is not the role for p44’s E3 Ub Ligase. It
is suggested that Ssl1-mediated ubiquitin ligase function targets
unknown transcription activator proteins to mediate the DNA damage
response, as mutations introduced in this RNF domain in Ssl1 leads to a
reduction in transcription of DNA repair genes in response to exposure
to DNA damage (Takagi et al., 2005). Whether the ubiquitylation-mediated
transcription response directly affects DNA repair has not been
analyzed.